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Biomedical subjects

K Lukowiak

Publications and source records attributed to K Lukowiak.

102 records · Page 6Linked to original sources
PubMed1978

Picrotoxin prevents habituation of the gill withdrawal reflex in Aplysia.

The gill withdrawal reflex evoked by tactile stimulation of the siphon in Aplysia habituates with repeated presentation of the stimulus. This adaptive behaviour is mediated by the integrated activity of the central (CNS) and peripheral (PNS) nervous systems. The PNS mediates the basic reflex and its habituation while the CNS exerts both suppressive and facilitatory control over the PNS. This results in greater adaptability of the reflex behaviours. In young Aplysia the CNS control is absent and this is due to the imcomplete development of pathways in the CNS. In an attempt to identify the pathway an attempt was made to manipulate the CNS's suppressive influence by agents which antagonize putative neurotransmitters. The application of picrotoxin-containing seawater over the CNS removed the CNS's suppressive influence but not its facilitatory influence. Thus the reflex amplitude was increased, the reflex latency decreased, and repeated stimulation did not result in habituation. This effect of picrotoxin was completely reversible. It is thus proposed that gamma-aminobutyric acid, a putative neurotransmitter, plays an important role in the mediation of the CNS's suppressive influence.

Animals↗
PubMed1977

CNS control of the PNS-mediated gill withdrawal reflex and its habituation.

Removal of the branchial (Br) nerve input to the gill significantly reduced the latency and increased the amplitude of the gill withdrawal reflex evoked by siphon stimulation. Further, after Br removal repeated siphon stimulation which previously resulted in habituation now resulted in facilitation of the flex. However, the synaptic input to gill motor neurons in the abdominal ganglion continued to decrement as before. In preparations without the peripheral nervous system (PNS), removal of Br did not produce similar results. The gill withdrawal reflex and its habituation are mediated by the PNS, but the CNS exerts facilitatory and suppressive control. Thus, changes in synaptic efficacy to gill motor neurons in the abdominal ganglion are not the ultimate cause of gill reflex habituation. Habituation is the result of adaptive neural processes which occur together in the abdominal ganglion, the PNS, and the peripheral terminations of the central motor pathways to the gill. Therefore, in any analysis of the underlying neural mechanisms of habituation all these loci must be included and taken into account.

Animals↗
PubMed1975

Habituation and dishabituation mediated by the peripheral and central neural circuits of the siphon of Aplysia.

The siphon withdrawal response evoked by a weak tactile (water drop) or light stimulus is mediated primarily by neurons in the siphon. Central neurons (abdominal ganglion) contribute very little since the response amplitude and latency are not changed following removal of the abdominal ganglion. Similarly, habituation and dishabituation of this withdrawal response are not different after removal of the abdominal ganglion, indicating that the peripheral neural circuit in the isolated siphon can mediate habituation itself, and thus has many of the properties attributed to central neurons. Response evoked by electrical stimulation of the siphon nerve habituate, depending upon the stimulus intensity and interval. These habituated responses may be dishabituated by tactile or light stimulation of the siphon. These results show that each neural system, peripheral and central, has an excitatory modulatory influence on the other. Normally adaptive siphon responses must be shaped by the integrated activity of both of these neural systems.

Animals↗
PubMed1972

Habituation and dishabituation: interactions between peripheral and central nervous systems in Aplysia.

The withdrawal response of the isolated siphon of Aplysia habituates to a light stimulus and dishabituates to a tactile stimulus, and vice versa, with or without connections to the central nervous system. The peripheral nervous system can dishabituate or enhance the response mediated by the central nervous system and vice versa. Normally the adaptive siphon withdrawal response of the intact animal must be mediated by the integrated activity of the peripheral and central nervous systems.

Action Potentials↗
PubMedDate not supplied

Urotensin I-like immunoreactivity in the central nervous system of Aplysia californica.

In the present study the occurrence and localization of urotensin I (UI, a corticotropin releasing factor-like peptide) in the CNS of Aplysia californica were investigated by immunocytochemistry and radioimmunoassay. The RIA cross-reactivity pattern indicated that the UI antiserum used recognized an epitope in the C-terminal region of the UI, but it did not cross-react with mammalian corticotropin-releasing factor (CRF) and partially recognized sauvagine (SVG, a frog CRF-like peptide). The use of CRF-specific and sauvagine-specific antisera failed to give positive immunostaining. The application of UI antiserum (which does not cross-react with CRF in RIA) gave a positive staining, which was blocked by synthetic sucker (Catostomus commersoni) UI, but not by rat/human CRF (10 microM). On the basis of immunostaining and RIA parallel to fish UI displacement curves of cerebral ganglia extracts, the unknown UI/CRF-like substance in the Aplysia ganglia is likely to have greater homology with sucker UI than with the known CRF peptides. Urotensin I-immunoreactive (UI-ir) neurons were seen mainly in the F neuron clusters, located in the midline and rostrodorsal portion of the cerebral ganglia. Few UI-ir neurons were also found in the C and D neuron clusters of the cerebral ganglia, as well as in the left pleural and abdominal ganglia. In addition, numerous fine and coarse, and beaded UI-ir fibers were found in the cerebral commissure. UI-ir fibers were also seen in the neuropile of the buccal, pedal and pleural ganglia, and abdominal ganglion. A cuff-like arrangement of UI-ir fibers was seen in the supralabial nerves.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Distribution and coexistence of urotensin I and urotensin II peptides in the cerebral ganglia of Aplysia californica.

Urotensin I (UI) and urotensin II (UII) were demonstrated in the cerebral ganglia of Aplysia californica by applying immunocytochemical and radioimmunoassay procedures. Sequential analysis of adjacent sections of the cerebral ganglia of Aplysia demonstrated that the UI-immunoreactive (UI-IR) neurons of the F cluster of the cerebral ganglia also contained UII immunoreactivity (UII-IR). Both UI-IR and UII-IR were also observed in a cuff-like arrangement of fibers surrounding the proximal portion of the supralabial nerve, as well as in a few fibers in the anterior tentacular nerves. The UI-IR perikarya of the cerebral ganglia appeared to project to the entire CNS of Aplysia, but the UII-IR fibers appeared only in the neuropile and commissure of the cerebral ganglia. The UI-IR staining was abolished by previous immunoabsorption of the UI antiserum with sucker (Catastomus commersoni) UI, but not with ovine corticotropin-releasing factor (CRF), rat/human CRF, or goby (Gillichthys mirabilis) UII. Immunostaining with UII antiserum was quenched by goby UII, but not by sucker UII-A, UII-B, UII-A(6-12), or carp (Cyprinus carpio) UII-alpha and UII-gamma. The UII staining was not abolished by UI or somatostatin. The F cluster was not stained when a somatostatin antiserum was applied. Radioimmunoassay of dilutions of cerebral ganglia extract, using UII antiserum, revealed a parallel displacement curve to synthetic goby UII.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Context learning and the effect of context on memory retrieval in Lymnaea.

Aerial respiratory behavior in Lymnaea was operantly conditioned so that the animals perform aerial respiration significantly less often. Using the standard training procedure (pond water made hypoxic by bubbling N2 through it) both food-deprived and fed animals learned and exhibited long-term memory (LTM). However, food-deprived animals exhibited neither learning nor memory when trained under a condition in which the hypoxic pond water also contained a food odorant (carrot, the food-odorant procedure). Fed animals, however, learned and exhibited LTM with the food-odorant procedure. Thus, the presence of the food odorant per se did not prevent learning or the establishment of LTM. Further experimentation, however, revealed that the ability of the snails to have recall (i.e., memory) for the learned behavior was dependent on the context in which memory was tested. That is, if animals were trained with the food-odorant procedure they could only exhibit recall if tested in the food-odorant context and vice versa with the standard training procedure. Thus, although fed animals could learn and show LTM with either training and testing procedure, LTM could only be seen when they were tested in the context in which they were trained.

Air↗
PubMedDate not supplied

Operant conditioning in Lymnaea: evidence for intermediate- and long-term memory.

Aerial respiration of the pond snail, Lymnaea stagnalis, can be operantly conditioned; however, the parameters necessary to produce long-term (LTM) or intermediate term memory (ITM) have not previously been investigated. We conducted training using procedures that varied in the duration of the training session, the number of training sessions per day or the amount of time between subsequent training sessions (SI). We found that by varying the duration and frequency of the training session learning could be differentially produced. Furthermore, the ability to form LTM was dependent not only on the duration of the training session was also the interval between training sessions, the SI. Thus it was possible to produce ITM, which persists for up to 3 hr, and not form LTM, which persists at least 18 hr. Learning, ITM, and LTM can be differentially produced by altering the SI, the duration of the training session, or the number of training sessions per day. These findings may allow us to begin to elucidate the underlying neural mechanisms of learning, ITM, and LTM.

Animals↗
PubMedDate not supplied

Trophic factor-induced plasticity of synaptic connections between identified Lymnaea neurons.

Neurotrophic factors participate in both developmental and adult synaptic plasticity; however, the underlying mechanisms remain unknown. Using soma-soma synapses between the identified Lymnaea neurons, we demonstrate that the brain conditioned medium (CM)-derived trophic factors are required for the formation of excitatory but not the inhibitory synapse. Specifically, identified presynaptic [right pedal dorsal 1 (RPeD1) and visceral dorsal 4 (VD4)] and postsynaptic [visceral dorsal 2/3 (VD2/3) and left pedal dorsal 1 (LPeD1)] neurons were soma-soma paired either in the absence or presence of CM. We show that in defined medium (DM-does not contain extrinsic trophic factors), appropriate excitatory synapses failed to develop between RPeD1 and VD2/3. Instead, inappropriate inhibitory synapses formed between VD2/3 and RPeD1. Similarly, mutual inhibitory synapses developed between VD4 and LPeD1 in DM. These inhibitory synapses were termed novel because they do not exist in the intact brain. To test whether DM-induced, inappropriate inhibitory synapses could be corrected by the addition of CM, cells were first paired in DM for an initial period of 12 hr. DM was then replaced with CM, and simultaneous intracellular recordings were made from paired cells after 6-12 hr of CM substitution. Not only did CM induce the formation of appropriate excitatory synapses between both cell pairs, but it also reduced the incidence of inappropriate inhibitory synapse formation. The CM-induced plasticity of synaptic connections involved new protein synthesis and transcription and was mediated via receptor tyrosine kinases. Taken together, our data provide the first direct insight into the cellular mechanism underlying trophic factor-induced specificity and plasticity of synaptic connections between soma-soma paired Lymnaea neurons.

Animals↗
PubMedDate not supplied

Neuronal mechanisms of learning in an in vitro Aplysia preparation: sites other than the sensory-motor neuron synapse are involved.

Classical conditioning of the gill withdrawal reflex can be demonstrated in two different in vitro Aplysia preparations. The data obtained show that as conditioning of the gill withdrawal reflex proceeds there are changes in synaptic efficacy at the central sensory-motor neurone synapse. These changes in synaptic efficacy, however, are not necessary nor are they sufficient for the observed changes in gill reflex behaviour. Changes must be occurring at other loci within the nervous system to mediate the associative learning. We hypothesized, based on data obtained from one type of in vitro preparation, that changes occur in the ability of the motor neurone to elicit a gill withdrawal response as a result of classical conditioning training. In order to test this hypothesis we depolarized an identified gill motor neurone before and after classical conditioning and found that the motor neurone's ability to elicit a gill movement was facilitated following classical conditioning training. In control preparations that received an explicitly unpaired stimulus paradigm (which does not lead to classical conditioning of the reflex) there was a decrease in the efficacy of a gill motor neurone to elicit a gill withdrawal response. There are a number of possible sites within the integrated central (CNS) and peripheral (PNS) nervous systems where changes could occur to bring about the alterations in motor neurone efficacy. Our results suggest that changes in neuronal activity which underlie learning occur at multiple sites within the nervous system and that a complete understanding of the mechanisms of associative learning can only be obtained when all of these sites are taken into account.

Animals↗